Magnetic short-circuiting switch.



L. & H. L. BRADLEY.

MAGNETIC SHORT CIRCUETING SWITCH.

APPLICATION FILED JULY 18, 1913.

1,151,241. Patented Aug. 24,1915.

WITNESSES:

IN VENTORS A TTORNE 1L9 ITED STATES PATENT OFFICE.

LYNDF BRADLEY AND HARRY L. BRADLEY, OF MILWAUKEE, WISCONSIN.

MAGNETIC SHORT-CIRCUITING SWITCH.

To all whom it may concern Our invention relates to improvements in magnetic short circuiting switches.

The 'ob]ect of our invention is to provide means for controlling an automatic motor -starter in such a manner that it W111 automatically protect the motor at all times and under all conditions when used in combina- 1 tion with-reversing switches, dynamic brakingsystems. and speclal control systems, using the so-called operators' switch or master switch. r

More particularly, the ob ect of our invention is to equip amotor starter of that type having a compressible resistance medium for controlling the current to the motor with means for automatically making the necessary resistance changes required for the protection of the motor more rapidly than it is possible for the operator to move the reversing switch or any lever by which the operator may change the working'circuits of'the motor.

It will be understood that if a motor starter is connected with a reversible motor,

it is virtually essential that when the reversing switch is thrown into the reverse position with the motor running at full speed, the starter must immediately insert resistancein the power circuit to keep the flow of current within safe limits while the motoris being brought to a stop, after which the resistance interposed by the starter must be gradually removed so that the motor may be brought up to the required speed in the reversed direction. Our inven tion contemplates the provision of automatic means for accomplishing these results in connection with a starter having compressible resistance columns, by removing the pressure from the resistance columns as soon as. the required speed of the motor is attained, the current to the motor having been first shunted from said columns. Shunting the columns from the circuit is accomplished in our improved apparatus by means of a magnetic switch which is opened to insert the resistance columns into the cir- Specification of Letters Patent.

Applicationfiled .r'uiy 18, 1913.

preferably composed of graphitedisks similartothose described in our former patent for a resistance device, Number 1054902, dated March 4th, 1913. The resistance of these columns decreases under pressure. I In our improved construction, pressure is applied to the columns by transmitting motion from the plunger 2 of solenoid 3, through bell crank 4 and an equalizing plate or bar 5, having universal joint connection at 6 with one arm of the bell crank and arranged to bear upon movable electrodes 7 which pass into the tubes and bear respectively against the ends of the graphite columns. These parts are mounted upon a switch board a, which is also provided with a magnetic line switch 12, an actuating solenoid 9 therefor, an accelerating relay 13, over-load relay 14, magnetic switch 15, controlled by a solenoid 23, and a compound magnetic circuit relay 19.

The several elements above mentioned are organized and electrically connected to operate as follows :-To start the motor A, a

push button or switch lever B will be actu-- -12 closed after the starting button B has been released and the contacts 8 separated. The operation of switch 12, as above ex-'' plained, also closes contacts E, whereupon the armature of motor A will receive cur-- rent from line C through switch '12, the

flexible jumper 30 connected to tongi'ie 16 carried by switch lever 15,, but insulated therefrom. In starting position this flexi ble jumper 30 is electrically connected witlr the coil of solenoid 3, through contact 17 and a circuit will therefore be established simultaneously with the armature and field circuits, above described, from lever 12 through tongue 34, contact flexible jumper 30, tongue 16, contact 17, the coil of solenoid 3, bar 18, controlled by accelerating relay 18, and thence to the line D at i d. The current in this circuit energizes solenoid 3 and draws plunger 2 downwardly, compressing the resistance columns as above explained. gradually decreases their resistance with a consequent graduated increase of current flow in the motor armature circuit until such flow reaches a volume suficient to energize the coil of accelerating relay 13, whereupon bar 18 will be lifted by the magnetic pull upon the relay core.v When bar 18 is thus lifted, the circuit through the winding of solenoid 3 is broken, said solenoid is immediately ,deenergized, and the increase of pressure upon the resistance columns ceases. The motor continues to accelerate and increase its counter electro 'motive force, and

the plunger 2 also tends 'to return to its initial position, thus relieving the columns 1 to some extent from pressure and increas ing their resistance. These two features quickly reduce the armature current to the point where the accelerating relay 13 is sufliciently decnergized to'permit bar 18 to again close said circuit through rhcostat solenoid 3 to again compress the resistance columns. This alternating action of the accelerating relay 13 and rheostat solenoid 3, will. be repeated with sullicient rapidity so that the armature current will remain substantially at the point to which the accelerating relay 13 set, or adjusted until a stage is reached here the drop in voltage across the resistance units becomes low enough to allow the compound relay 1!) to unlock, whereupon this relay operates to close the circuit across points 21. The relay 1.) is of the well. known compound magnetic circuit type similar to that shown at S-l), Sc, in U. S.- patent to Hall, numbered 1053494, dated February 18, 1913, or that shown at L in The-compression of the columns .as compared to the U. S. patent to Eastwood, numbered 1040292, dated October 8, 1912. It is locked open by the excess of magnetic flux when its operat ing coil .is subjected to a voltage greater than .that under which it is designed to operate,

l5 to the motor, thus shunting or short circuiting the resistance columns 1 from the armature circuit. The coil of relay 19 will also be short cir'cuited by switch bar 15, and relay 19 will therefore open or disconnect points 21 electrically as soon as the winding of magnetic switch 23 is energized. To prevent this electrical separation of contacts 21't'rom deenergizing the winding of magnetic switch 23, contact 24 is connected through a suitable resistance 33 with the winding of magnetic switch 23, and the arrangement is such that when switch bar 15 swings to close contacts G, tongue 16 will swing downwardly to contact 24, thus permitting current delivery to the winding of magnetic switch 23 from line C, through switch bar- 12, lip 34, contact 32, flexible jumper 30, tongue 16, contact 21, resistance 33, and the winding of switch 23 to line I). This keeps the n'iagnetic switch 23 energized after relay 19 has opened the original circuit through this switch.

It will be observed that when tongue 16 moves downwardly to contact 24,- it separates frhm contact 17 which originally connected 'it'with the winding of rheostat solenoid 3. The circuit through this winding is therefore broken as soon a switch bar 15 closes contacts G. This relieves the pressure upon the resistance columns 1, and such pressure may be wholly removed by spring 31, which is arranged to actuate bell crank 4, whereby equalizer plate 5 is retracted and the core 2 ofthe rheostat solenoid 3 lifted. This restores resistance units 1 to their condition of maximum resistance, and also prevents consumption of current in the rheostat solenoid (and consequent heating) when the 'rheostat is not regulatingthe motor. When it is desired to stop and start the motor in quick succession,-it is, found that this'retrieving of the rheostat solenoid is 01 great advantage, as these solenoids are of considerable size and slow in'their action smaller solenoids 9 and ot the magnetic line i energizing-rheostat solenoid 3 and returning the resistance units to their condition of switches. By del maximum resistance, the starter is in nor-' mal condition of readiness to again regulate the acceleration of the motor the instant 'magnetic line switches 12 and 15 are opened.

cuit in connection with the above described cycle of current regulating operations.

VVhen-it is desired to stop the motor and restore the starting mechanism to its initial position, the button H is pushed to close contacts 26 and thereby short circuit the coil of magnetic switch 9 which, when deenergized, allows switch bar 12 to move to open position, thus shutting ofi' current from the motor and de'e'nergizing magnetic switch 23.

lVe believe we are the first to provide means for automatically utilizing variations in voltage through a variable resistance current regulating device to shut out such resistance and restore it to normal position ready for automatic operation we protect the motor against injury from intermittent A. companion application bearing even date herewith, filed July 18, 1913, Serial No. 779,694 shows and describes some of the features illustrated in this application, with claims for an alternative structure designed to accomplish the same general purpose sought to be accomplished in the apparatus herein described. In the companion application, however, the construction is such that the shuntingof the resistance columns and rheostat solenoid from the main motor circuit, is dependent upon the attainment of a predetermined pressure upon such columns, whereas in this application it is dependent upon the attainment of predetermined current conditions in the circuit.

lVhile we have shown and described our invention as involving the use of a compound magnetic circuit relay in shunt with a compressible resistance column, we do not thereby intend to limit the scope of our claims entirely to this arrangement, since an ordinary electro-magnetic switch or relay may be used in shunt with a motor armature or some other portion of the circuit, to accomplish the same purpose of cutting out, short circuiting or otherwise removing the resistance member when the rise in potential through such portion of the circuit reaches a predetermined degree.

1. An automatic electrical controlling apparatus, comprising the combination with a mainelectrical circuit, of a current controlling variable resistance, means for progressively reducing the resistance of said medium. means for utilizing the voltage drop across said medium to remove said medium from the main circuit after a predetermined drop in the voltage, and means for automatically restoring said medium to maximum resistance when it is so removed from the main circuit.

2. The combination with a main electrical circuit, of a compressible resistance column, electro-magnetic means for compressing the same, means for removing said resistance column from the main circuit, and an electro-magnetic device controlling said removing means and adapted to operate at a predetermined drop in voltage across the resistance-column, together with means, controlled by said device, for denergizing the electro-magnetic compressing means and re- -storing said column to low pressure condition.

3. The combination with electrically .driven apparatus and a main circuit-there for, of a compressible resistance member, a manually controlled electro-magnetic device for closing said main circuit through said compressible resistance member, electro-magnetic means, in shunt with said main circuit, for compressing said resistance member, an electro-magnetic relay operable under a predetermined difference in potential and connected in parallel with said resistance member, an electroanagnetic switch for removing said resistance member fromthe circuit, and means actuated by the relay for energizing said last mentioned switch.

4. The combination with electrically driven apparatus and a main circuit therefor, of a compressible resistance member, a manually controlled eleotro-magnetic device for closing said main circuit through said compressible resistance member, electromagnetic means, in shunt with said main circuit, for compressing said resistance member, an electro-magnetic' relay operable under predetermined electrical conditions and connected inshunt with said resistance member, an electro-magnetic switch for removing said resistance member from the circuit, and means actuated by the relay for energizing said last mentioned switch, and means controlled by said last mentioned switch for relieving said resistance member from pressure.

5. The combination with a compressible resistance medium, of an electro-magnetic device operable under predetermineddifference in potential across the resistance medium to automatically relieve said medium of pressure.

6. The combination with a main circuit of a compressible resistance medium and an electro-ma-gnetic device, operable under predetermined dili'erence in potential across the resistance medium, to automatically remove said medium from the main circuit.

' 7 The combination with a main electrical circuit, of a variable resistance member, a manually controlled switch for establishing the main circuit through said member, an electricallycontrolled automatic switch for establishing the main circuit independently of said member, and an electro-magnetic relay controlling the last mentioned switch, said relay being adjusted to operate under predetermined variations in potential, together with electro-magnetic means for vary ing the resistance of said member and permitting restoration of maximum resistance capacity, simultaneously with the closing of the automatic switch, substantially as de scribed.

S. The combination with a mam circuit,

of a compressible resistance member, means for compressing the same. electro-magnetlc means for relieving said member from pres sure and removing itfrom the main circuit, said electromagnetic means being operative only under predetermined conditions of electro-motive force across said member. I

9. In an electric current controller, the combination with a main circuit, of a resistance medium adapted to be included in said circuit, means for compressingsaid'medium and means for automatically removing said medium from said circuit when the voltage drop across said medium is less than a predetermined amount.

10. In an electric current controller, the combination with a main circuit, of a resistance medium adapted to be included in said circuit, means for producing pressure on said medium, 'electro magnetic means operable under a predetermined voltage drop across said medium and the connections controlled thereby, and adapted to remove said resistance medium from said circuit when the voltage drop across said medium be comes less than a predetermined amount.

In testimony whereof we affix our signatures in the presence of two witnesses.

LYN DE BRADLEY. ARRY L. BRADLEY.

Witnesses:

C. J. CARLSON, P. W. KAUFMANX.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). G. 

